The present invention relates to electric power plants and more particularly to improved gasifier-combined cycle plants.
In a gasifier-combined cycle power plant, a gasifier processes fossil fuel such as pulverized coal or oil to generate a fuel gas for use in operating one or more gas turbine sets. In turn, the gas turbine exhaust is directed through heat recovery steam generator means to produce steam for operating a steam turbine. Electric generators are driven by the turbines to produce the plant power output.
The gasification process includes a cleanup step which enables the plant to satisfy environmental restrictions on atomspheric discharge. The enengy exchanges which occur throughout the plant processes generally enable the plant efficiency to be relatively high, especially for intermediate plant duty. An example of a prior art plant of the type described is set forth in a paper entitled PACE-SGP Oil Gasification Combined Cycle For Power Generation and presented to the American Power Conference in Chicago in April, 1974. Another prior art article entitled Recent Experimental Results on Gasification Combustion of Low BTU Gas for Gas Turbines and published in Combustion in April 1974 describes a plant in which an alternative gasification process is used. Various prior art U.S. patents relate to this subject matter area including Schorner No. 2,675,672, Marion No. 3,866,411, Archer No. 3,804,606, Rudolph No. 3,765,167, Blaskowski No. 3,849,662 and Krieb No. 3,704,587. At pages 16 and 17 of the May 1973 issue of Gas Turbine World there is also disclosed a gasification combined cycle system.
There has generally existed a need to improve the manner in which the gasifier and the combined cycle are integrated to function as a unitary power plant. Specifically, there has existed a need to improve the way in which air is supplied to the gasifier system from the gas turbine apparatus, the way in which generated fuel gas is processed for use in the gas turbine apparatus, and the way in which stable operation is provided for the gasifier system as plant laod changes are made. The present invention is directed to these areas of improvement. No representation is made that the prior art cited herein is the best prior art nor that the interpretations placed on it are not rebuttable.